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Date: Fri, 12 Sep 2014 01:45:03 +0400 From: Solar Designer <solar@...nwall.com> To: discussions@...sword-hashing.net Subject: Re: [PHC] A review per day - Lyra2 On Thu, Sep 11, 2014 at 07:35:31PM +0100, Samuel Neves wrote: > On the 32-bit version of the permutation, it is straightforward to replace vpaddd with vpmulld + vpaddd. As discussed before, (V)PMULLD has 10 cycles latency on Haswell and 11 cycles on Silvermont/Avoton, as opposed to 5 cycles for other multiply instructions on the same CPUs. But I guess this may be acceptable, if this specific approach has other advantages over possible alternatives. On most other CPUs, (V)PMULLD is fast. In yescrypt, I chose to avoid the need for this instruction, though, opting to rely on 32x32->64 multiplies instead, which is (V)PMULUDQ (but twice fewer of these fit per vector). Alexander
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